Visa and American Express are the two main brands of travelers checks. Travelers checks can be purchased at exchange bureaus or any major banking institution.
Travelers checks have security features to make it easier to tell if a travelers check is authentic or not. Check for a shiny strip along the top, middle or bottom (depending on the brand) and it should not be dull. Hold the check up to the light to look for a watermark. All checks have a watermark on the paper that can only be seen with light.
The signature is a key factor in the authenticity of a travelers check. Check to make sure the signature on the back of the check is signed in front of the clerk and that it matches the signature on the front of the check. (The front of the check should be pre-signed; this is done at the point of purchase from the bank.) Look at photo identification to match the name to the person on the check.
Check to make sure the check's paper is thin like a personal check--most fake travelers checks are thicker--and the printing on the check is also thicker with a raised texture.
If there is any problem with a check or is suspected to be a fake, call the bank that issued the check. All banks are required to keep files of these transactions.